The subject of the invention is a device for advancing the workpiece in an electro-erosive processing by a wire-like electrode which is threaded into a starting bore in the workpiece and is drawn through by the drive and guide system. A path of the relative movements between the workpiece and the electrode is controlled by means of an electric control system. The workpiece is fixed at a portion of the workpiece which is not to be processed to a cross-coordinate support which can be moved in both directions of movement on a clamp bearing.
Wire erosion machines, in particular those which are numerically controlled, can be used with great advantage for cutting complicated outer or inner contours on electrically conductive workpieces. As is known, during the processing operation, wire-like or strip-like electrodes and workpieces move relative to one another. The electrode is drawn off from a feed roller, moves past the workpiece which is to be processed, and passes to a drive device which consists of a pair of rollers which impart a uniform forwards motion to the electrode. Finally, the electrode is rewound onto a roller or chopped into small pieces which fall into a collector container. A sensor which is arranged between the feed rollers and workpiece checks for the presence of a slight mechanical tensile stress in the electrode. If the tensile stress is not present due to a disturbance, the sensor instigates the disconnection of the electrical voltage which produces the erosion sparks, and halts the numerical control and the advance of the electrode.
For the relative movement between workpiece and electrode, the workpiece together with the component which is not to be processed is clamped to a cross-coordinate support. The electrode is threaded through a starting bore in the workpiece and drawn through by the drive and guide system arranged following the workpiece. The movements of the support and thus of the workpiece in the two horizontal directions of movement are triggered by the electrical control system which is fed with the program for the contour to be processed in the workpiece via a punched strip. The workpiece which is to be processed consists of a plate or of a stack of plates arranged one above another from which the programmed contours are cut out by spark erosion using a wire-like copper electrode. The known feed device used in commercially available wire erosion machines has the disadvantage that during the last cutting phase of a contour, the material which has been cut out is bent downwards on account of its weight and becomes twisted. This results in penetration points on the workpiece, short circuits and occasionally the breaking off of the electrode. The workpiece is then unserviceable. In the event of a short-circuit, automatic further erosion of the contour is impossible. An operator must monitor the last cutting phase of each contour during the erosion.